I've been busy
Same friend took Maverick and integrated it into his Longshot (then painted it black, red, and gold, named "Jericho" due to the Iron Man color scheme), so I had him help me integrate one of my Mavs into the Retaliator barrel extension that I never use (Longstrike barrel ftw). He didn't have enough putty at the time, so it's just a quick job so far (actually, the Maverick fell off, since the putty didn't have a good enough grip). I plan on making it better, then painting the Mav blue with the obligatory white highlights.
He also had a broken Vulcan bolt, so I took one of the plastic handles of that and hot glued in onto the slide of my Retaliator so I could top-mount rail accessories while still being able to prime it. It actually makes it a heck of a lot easier to prime in general. (I did this one a while ago, actually, but I feel inclined to include all the big mods I've done so far.)
tl;dr: Retaliator is great for modding, every arsenal should include a Roughcut